In the attached file, UnrollSrf fails without an explanation. The surface was made from straight lofts between two curves so it can unroll mathematically.
Problem Unroll.3dm.zip (38.3 KB)
Smash does not work either.
Straight lofts or ruled surfaces between two curves do not necessarily produce developable surfaces. The hyperboloid, imaged below, is a classic example.
Try using the DevLoft command instead of Loft.
